12 U-series dating

The intermediate nuclides in the U)Pb and Th)Pb decay series have very short half-lives in comparison with their parents, and are usually ignored in the Pb isotope dating methods. However, their short half-lives make these nuclides useful for dating Pleistocene geological events which are too old to be well resolved by the radiocarbon method and too young to be well resolved by decay schemes with long half-lives. The manner in which U-series nuclides can fill this ‘dating gap’ is shown in Fig. 12.1. Generally they are most useful for dating events of similar age to their half-life.

Fig. 12.1. Diagram showing the dating ranges of different nuclides within the three U-series decay chains to show their utility. After Potts (1987).

12.1 Secular equilibrium and disequilibrium

A distinctive property of the U-series nuclides which sets them apart from other isotope dating schemes is that the radiogenic daughters are themselves radioactive. Hence, in a uranium-bearing system which has remained undisturbed for a few million years, a state of ‘secular equilibrium’ becomes established between the abundances of successive parent and daughter nuclides in the U and Th decay chains, such that the decay rate (or ‘activity’) of each daughter nuclide in the chain is equal to that of the parent:

Activity = 8₀n₀ = 8₁n₁ = 8₂n₂ = 8_Nn_N [12.1]

where 8₀ is the decay constant and n₀ is the number of atoms of the original parent, 8₁ and n₁ are the decay constant and abundance of the first daughter, and so on. It follows that the abundance of each nuclide will be directly proportional to its half-life (i.e. inversely proportional to its decay constant). The relevant parts of the decay chains are shown in Fig. 12.2.

Fig. 12.2. Part of the chart of the nuclides, in term of Z against N, to show species in the Th- and U-series decay chains and their half-lives. Useful species are indicated by double boxes. In early research on decay series nuclides, some species were given special names (e.g. ²³⁰Th = ionium). However, these are now obsolete.

During geological processes such as erosion, sedimentation, melting, or crystallisation, different nuclides in the decay series can become fractionated relative to one another, due to variations in their chemistry or the structural site they occupy. This results in a state of secular disequilibrium. Such a situation can be utilised in two different ways as a dating tool, called respectively the ‘daughter-excess’ and ‘daughter-deficiency’ dating methods.

In the daughter-excess method, a deposit is formed with an excess of the daughter beyond the level which can be sustained by the abundance of its parent nuclide. Over time, the excess or ‘unsupported’ daughter decays back until secular equilibrium with its parent is restored. If the original fractionation can be estimated, the age of the deposit can be calculated by the progress of decay of the excess.

In the daughter-deficiency method, chemical fractionation during the formation of a deposit causes it to take up a radioactive parent but effectively none of its daughter. The age of the deposit can then be determined by measuring the growth of the daughter, up to the point when its abundance is within error of secular equilibrium of the parent.

Using high-precision mass spectrometric data (section 12.2.1) the useful dating range of U-series nuclides may be up to seven half-lives, but other factors may impose lower limits. Table 12.1 summarises some of the more important U-series dating methods. Note that in this chapter, all nuclide abundances are given as activities unless stated otherwise.

Table 12.1 U-series dating methods

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Method Measurement t_1/2,kyr Range,kyr Application

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Daughter excess

²³⁴U)²³⁸U ²³⁴U decay 245.3 < 1500 Coral

²³⁰Th ²³⁰Th " 75.7 < 500 Deep sea sedimentation rates

²³¹Pa ²³¹Pa " 32.8 < 200 ditto

²¹⁰Pb ²¹⁰Pb " 0.022 < 0.1 Recent sedimentation

Daughter deficiency

²³⁰Th)²³⁴U ²³⁰Th accum. 75.7 < 500 Marine & fresh-water carbonate, volcanics

²³¹Pa)²³⁵U ²³¹Pa " 32.8 < 200 Closed-system test for ²³⁰Th

²²⁶Ra)²³⁸U ²²⁶Ra " 1.6 < 10 ditto

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References

Allegre, C. (1964). De l’extension de la methode de calcul graphique concordia aux mesures d’ages absolus effectues a l’aide du desequilibre radioactif. C. R. Acad. Sci. Paris 259, 4086–9.

Asmerom, Y. and Edwards, R. L. (1995). U-series isotope evidence for the origin of continental basalts. Earth Planet. Sci. Lett. 134, 1–7.

Bard, E., Fairbanks, R. G., Hamelin, B., Zindler, A. and Hoang, C. T. (1991). Uranium-234 anomalies in corals older than 150,000 years. Geochim. Cosmochim. Acta 55, 2385)90.

Benoit, G. and Hemond, H. F. (1991). Evidence for diffusive redistribution of ²¹⁰Pb in lake sediments. Geochim. Cosmochim. Acta 55, 1963)75.

Bischoff, J. L. and Fitzpatrick, J. A. (1991). U-series dating of impure carbonates: an isochron technique using total-sample dissolution. Geochim. Cosmochim. Acta 55, 543)54.

Bloom, A. L., Broecker, W. S., Chappell, J. M. A., Matthews, R. K. and Mesolella, K. J. (1974). Quaternary sea level fluctuations on a tectonic coast: new ²³⁰Th/²³⁴U dates from the Huon Peninsula, New Guinea. Quaternary Res. 4, 185)205

Bourdon, B., Joron, J.-L. and Allegre, C. J. (1999). A method for ²³¹Pa analysis by thermal ionization mass spectrometry in silicate rocks. Chem. Geol. 157, 147–51.

Bruland, K. W., Bertine, K., Koide, M. and Goldberg, E. D. (1974). History of metal pollution in Southern California coastal zone. Envir. Sci. Tech. 8, 425)32.

Chabaux, F., Cohen, A. S., O’Nions, R. K. and Hein, J. R. (1995). ²³⁸U–²³⁴U–²³⁰Th chronometry of Fe–Mn crusts: growth processes and recovery of thorium isotopic ratios of seawater. Geochim. Cosmochim. Acta 59, 633–8.

Chabaux, F., O’Nions, R. K., Cohen, A. S. and Hein, J. R. (1997). ²³⁸U–²³⁴U–²³⁰Th disequilibrium in hydrogenous oceanic Fe–Mn crusts: palaeoceanographic record or diagenetic alteration? Geochim. Cosmochim. Acta 61, 3619–32.

Chase, Z., Anderson, R. F., Fleisher, M. Q. and Kubik, P. W. (2002). The influence of particle composition and particle flux on scavenging of Th, Pa and Be in the ocean. Earth Planet. Sci. Lett. 204, 215–29.

Cheng, H., Edwards, R. L., Hoff, J., Gallup, C. D., Richards, D. A. and Asmerom, Y. (2000). The half-lives of uranium-234 and thorium-230. Chem. Geol. 169, 17–33.

Cheng, H., Edwards, R. L., Murrell, M. T. and Benjamin, T. M. (1998). Uranium thorium protoactinium dating systematics. Geochim. Cosmochim. Acta 62, 3437–52.

Chen, J. H., Edwards, R. L. and Wasserburg, G. J. (1986). ²³⁸U, ²³⁴U and ²³²Th in seawater. Earth Planet. Sci. Lett. 80, 241)51.

Cherdyntsev, V. V. (1969). Uranium-234. Atomizdat, Moscow. Translated by Schmorak, J. Israel Prog. Sci. Trans. (1971), 234 p.

Cherdyntsev, V. V., Kazachevskii, I. V. and Kuz’mina, E. A. (1965). Dating of Pleistocene carbonate formations by the thorium and uranium isotopes. Geochem. Int. 2, 794)801.

Cherdyntsev, V. V., Orlov, D. P., Isabaev, E. A. and Ivanov, V. I. (1961). Isotopic composition of uranium in minerals. Geochemistry 10, 927)36.

Cochran, J. K., Livingston, H. D., Hirschberg, D. J. and Surprenant, L. D. (1987). Natural and anthropogenic radionuclide distributions in the northwest Atlantic Ocean. Earth Planet. Sci. Lett. 84, 135–52.

Crozaz, G., Picciotto, E. and DeBreuck, W. (1964). Antarctic snow chronology with Pb-210. J. Geophys. Res. 69, 2597)604.

de Bievre, P., Lauer, K. F., Le Duigou, Y., Moret, H., Muschenborn, G., Spaepen, J., Spernol, A., Vaninbroukx, R. and Verdingh, V. (1971). In: Hurrell, M. L. (Ed.), Proc. Int. Conf. Chem. Nucl. Data, Inst. Civil Eng. Lond., pp. 221)5.

Edwards, R. L., Chen, J. H. and Wasserburg, G. J. (1987). ²³⁸U)²³⁴U)²³⁰Th)²³²Th systematics and the precise measurement of time over the past 500,000 years. Earth Planet. Sci. Lett. 81, 175)92.

Edwards, R. L., Cheng, H., Murrell, M. T. and Goldstein, S. J. (1997). Protactinium-231 dating of carbonates by thermal ionization mass spectrometry: implications for Quaternary climate change. Science 276, 782–6.

Edwards, R. L. and Gallup, C. D. (1993. Dating of the Devils Hole calcite vein. Science 259, 1626–7.

Edwards, R. L., Taylor, F. W. and Wasserburg, G. J. (1988). Dating earthquakes with high-precision thorium)230 ages of very young corals. Earth Planet. Sci. Lett. 90, 371)81.

Esat, T. M., McCulloch, M. T., Chappell, J., Pillans, B. and Omura, A. (1999). Rapid fluctuations in sea level recorded at Huon Peninsula during the penultimate deglaciation. Science 283, 197–201.

Frank, M., Eisenhauer, A., Bonn, W. J., Walter, P., Grobe, H., Kubik, P. W., Dittrich-Hannan, B. and Mangini, A. (1995). Sediment redistribution versus paleoproductivity change: Weddell Sea margin sediment stratigraphy and biogenic particle flux of the last 250 000 years deduced from ²³⁰Th_ex, ¹⁰Be and biogenic barium profiles. Earth Planet. Sci. Lett. 136, 559–73.

Gallup, C. D., Cheng, H., Taylor, F. W. and Edwards, R. L. (2002). Direct determination of the timing of sea level change during termination II. Science 295, 310–3.

Goldberg, E. D. (1963). Geochronology with Pb-210. In: Radioactive Dating. IAEA, Vienna, pp. 121)31.

Goldberg, E. D. and Bruland, K. (1974) Radioactive geochronologies. In: Goldberg, E. D. (Ed.) The Sea. vol. 5, Wiley Interscience, pp. 451)89.

Goldberg, E. D. and Koide, M. (1962). Geochronological studies of deep sea sediments by the ionium/thorium method. Geochim. Cosmochim. Acta 26, 417)50.

Grun, R. and McDermott, F. (1994). Open system modelling for U-series and ESR dating of teeth. Quaternary Geochron. (Quaternary Sci. Rev.) 13, 121–5.

Grun, R., Schwarcz, H. P. and Chadam, J. (1988). ESR dating of tooth enamel: coupled correction for U-uptake and U-series disequilibrium. Nucl. Tracks Radiat. Meas. 14, 237–41.

Henderson, G. M. (2002). Seawater (²³⁴U/²³⁸U) during the last 800 thousand years. Earth Planet Sci. Lett. 199, 97–110.

Henderson, G. M. and Burton, K. W. (1999). Using (²³⁴U/²³⁸U) to assess diffusion rates of isotopic tracers in ferromanganese crusts. Earth Planet. Sci. Lett. 170, 169–79.

Henderson, G. M. and O’Nions, R. K. (1995). ²³⁴U/²³⁸U ratios in Quaternary planktonic foraminifera. Geochim. Cosmochim. Acta 59, 4685–94.

Imbrie, J., Hays, J. D., Martinson, D. G., McIntyre, A., Mix, A. C., Morley, J., Pisias, N., Prell, W. and Shackleton, N. J. (1984). The orbital theory of Pleistocene climate: support from a revised chronology of the marine *¹⁸O record. In: Berger, A. L. et al. (Eds), Milankovitch and Climate, Part 1. Reidel, pp. 269)305.

Imbrie, J., Mix, A. C. and Martinson, D. G. (1993). Milankovitch theory viewed from Devils Hole. Nature 363, 531)3.

Ivanovich, M. (1982a). Spectroscopic methods. In: Ivanovich, M. and Harmon, R. S. (Eds), Uranium Series Disequilibrium Applications to Environmental Problems. Oxford Univ. Press, pp. 107)44.

Ivanovich, M. (1982b). Uranium series disequilibria applications in geochronology. In: Ivanovich, M. and Harmon, R. S. (Eds), Uranium Series Disequilibrium Applications to Environmental Problems. Oxford Univ. Press, pp. 56)78.

Jonas, M. (1997). Concepts and methods of ESR dating. Radiation Meas. 27, 943–73.

Karner, D. B. and Muller, R. A. (2000). A causality problem for Milankovitch. Science 288, 2143–4.

Kaufman, A. (1971). U-series dating of Dead Sea carbonates. Geochim. Cosmochim. Acta 35, 1269)81.

Kaufman, A. and Broecker, W. S. (1965). Comparison of Th-230 and C-14 ages for carbonate materials from lakes Lahontan and Bonneville. J. Geophys. Res. 70, 4039)54.

Kaufman, A., Broecker, W. S., Ku, T. L. and Thurber, D. L. (1971). The status of U-series methods of mollusc dating. Geochim. Cosmochim. Acta 35, 1155)83.

Kaufman, A. and Ku, T.-L. (1989). The U-series ages of carnotites and implications regarding their formation. Geochim. Cosmochim. Acta 53, 2675–81.

Kaufman, A., Ku, T.-L. and Luo, S. (1995). Uranium-series dating of carnotites: concordance between ²³⁰Th–²³¹Pa ages. Chem. Geol. (Isot. Geosci. Sect.) 120, 175–81.

Khlapin, V. G. (1926). Dokl. Akad. Nauka SSSR 178.

Koide, M., Soutar, A. and Goldberg, E. D. (1972). Marine geochronology with Pb-210. Earth Planet. Sci. Lett. 14, 442)6.

Krishnaswamy, S., Lal, D., Martin, J. M. and Meybek, M. (1971). Geochronology of lake sediments. Earth Planet. Sci. Lett. 11, 407)14.

Ku, T. L. (1965). An evaluation of the U²³⁴/U²³⁸ method as a tool for dating pelagic sediments. J. Geophys. Res. 70, 3457)74.

Ku, T. L. (1976). The uranium series methods of age determination. Ann. Rev. Earth Planet. Sci. 4, 347)79.

Ku, T. L., Bischoff, J. L. and Boersma, A. (1972). Age studies of Mid-Atlantic Ridge sediments near 42 ^oN and 20 ^oN. Deep-Sea Res. 19, 233)47.

Ku, T. L., Knauss, K. G. and Mathieu, G. G. (1977). Uranium in open ocean: concentration and isotopic composition. Deep-Sea Res. 24, 1005)17.

Ku, T. L. and Liang, Z. C. (1984). The dating of impure carbonates with decay-series isotopes. Nucl. Instr. Meth. in Phys. Res. A 223, 563)71.

Kumar, N., Gwiazda, R., Anderson, R. F. and Froelich, P. N. (1993). ²³¹Pa/²³⁰Th ratios in sediments as a proxy for past changes in Southern Ocean productivity. Nature 362, 45)8.

Li, W. X., Lundberg, J., Dickin, A. P., Ford, D. C., Schwarcz, H. P., McNutt, R. H. and Williams, D. (1989). High-precision mass-spectrometric uranium-series dating of cave deposits and implications for palaeoclimate studies. Nature 339, 534)6.

Ludwig, K. R., Simmons, K. R., Szabo, B. J., Winograd, I. J., Landwehr, J. M., Riggs, A. C. and Hoffman, R. J. (1992). Mass-spectrometric ²³⁰Th)²³⁴U)²³⁸U dating of the Devils Hole calcite vein. Science 258, 284)7.

Ludwig, K. R., Szabo, B. J., Moore, J. G. and Simmons, K. R. (1991). Crustal subsidence rate off Hawaii determined from ²³⁴U/²³⁸U ages of drowned coral reefs. Geology 19, 171)4.

Ludwig, K. R. and Titterington, D. M. (1994). Calculation of ²³⁰Th/U isochrons, ages, and errors. Geochim. Cosmochim. Acta 58, 5031–42.

Lundberg, J., Ford, D. C., Schwarcz, H. P., Dickin, A. P. and Li, W. X. (1990). Dating sea level in caves: reply. Nature 343, 217)18.

Luo, S. and Ku, T. L. (1991). U-series isochron dating: a generalised method employing total-sample dissolution. Geochim. Cosmochim. Acta 55, 555)64.

Luo, S. and Ku, T.-L. (1999). Oceanic ²³¹Pa/²³⁰Th ratio influenced by particle composition and remineralization. Earth Planet. Sci. Lett. 167, 183–95.

Mangini, A. and Diester-Haass, L. (1983). Excess Th-230 in sediments off NW Africa traces upwelling in the past. In: Suess, A. E. and Thiede, J. (Eds), Coastal Upwelling. Plenum. Part A, pp. 455)70.

McDermott, F., Grun, R., Stringer, C. B. and Hawkesworth, C. J. (1993). Mass-spectrometric U-series dates for Israeli Neanderthal/early modern hominid sites. Nature 363, 252)5.

Meadows, J. W., Armani, R. J., Callis, E. L. and Essling, A. M. (1980). Half-life of ²³⁰Th. Phys. Rev. C 22, 750)4.

Milankovitch, M. M. (1941). Canon of insolation and the ice age problem. Koniglich Serbische Akademie, Belgrade. Translation, Israel Prog. Sci. Trans.

Neff, U., Bollhofer, A., Frank, N. and Mangini, A. (1999). Explaining discrepant depth profiles of ²³⁴U/²³⁸U and ²³⁰Th_exc in Mn-crusts. Geochim. Cosmochim. Acta 63, 2211–18.

Osmond, J. K. and Cowart, J. B. (1982). Ground water. In: Ivanovich, M. and Harmon, R. S. (Eds), Uranium Series Disequilibrium Applications to Environmental Problems, Oxford Univ. Press, pp. 202)45.

Picciotto, E. G. and Wilgain, S. (1954). Thorium determination in deep-sea sediments. Nature 173, 632)3.

Pickett, D. A., Murrell, M. T. and Williams, R. W. (1994). Determination of femtogram quantities of protactinium in geological samples by thermal ionization mass spectrometry. Anal. Chem. 66, 1044–9.

Potts, P. J. (1987). Handbook of Silicate Rock Analysis. Blackie, 602 p.

Przybylowicz, W., Schwarcz, H. P. and Latham, A. G. (1991). Dirty calcites. 2. Uranium-series dating of artificial calcite)detritus mixtures. Chem. Geol. (Isot. Geosci. Sect.) 86, 161)78.

Rink, W. J. (1997). Electron spin resonance (ESR) dating and ESR applications in Quaternary science and archaeometry. Radiat. Meas. 27, 975–1025.

Rink, W. J., Schwarcz, H. P., Lee, H. K., Rees-Jones, J., Rabinovich, R. and Hovers, E. (2001). Electron spin resonance (ESR) and thermal ionization mass spectrometric (TIMS) ²³⁰Th/²³⁴U dating of teeth in Middle Paleolithic layers at Amud Cave, Israel. Geoarchaeology 16, 701–17.

Roberts, J., Miranda, C. F. and Muxart, R. (1969). Mesure de la periode du protactinium-231 par microcalorimetrie. Radiochim. Acta 11, 104–8.

Rosholt, J. N., Emiliani, C., Geiss, J., Koczy, F. F. and Wangersky, P. J. (1961). Absolute dating of deep-sea cores by the Pa-231/Th-230 method. J. Geol. 69, 162)85.

Rosholt, J. N., Shields, W. R. and Garner, E. L. (1963). Isotopic fractionation of uranium in sandstone. Science 139, 224)6.

Sackett, W. M. (1960). Protoactinium-231 content of ocean water and sediments. Science 132, 1761)2.

Sackett, W. M. (1964). Measured deposition rates of marine sediments and implications for accumulation rates of extraterrestrial dust. Ann. N.Y. Acad. Sci. 119, 339)46.

Sackett, W. M. (1966). Manganese nodules: thorium-230: protoactinium-231 ratios. Science 154, 646)7.

Santschi, P. H., Li, Y. H., Adler, D. M., Amdurer, M., Bell, J. and Nyffeler, U. P. (1983). The relative mobility of natural (Th, Pb and Po) and fallout (Pu, Am, Cs) radionuclides in the coastal marine environment: results from model ecosystems (MERL) and Narragansett Bay. Geochim. Cosmochim. Acta 47, 201)10.

Scholten, J. C., Botz, R., Mangini, A., Paetsch, H., Stoffers, P. and Vogelsang, E. (1990). High resolution ²³⁰Th_ex stratigraphy of sediments from high-latitude areas (Norwegian Sea, Fram Strait). Earth Planet. Sci. Lett. 101, 54)62.

Schwarcz, H. P. (1989). Uranium series dating of Quaternary deposits. Quaternary Int. 1, 7)17.

Schwarcz, H. P. and Blackwell, B. (1991). Archaeological applications. In: Ivanovich, M. and Harmon, R. S. (Eds), Uranium Series Disequilibrium Applications to Environmental Problems. 2nd Edn, Oxford Univ. Press, pp. 513)52.

Schwarcz, H. P. and Latham, A. G. (1989). Dirty calcites. 1. Uranium-series dating of contaminated calcite using leachates alone. Chem. Geol. (Isot. Geosci. Sect.) 80, 35)43.

Schwarcz, H. P. and Skoflek, I. (1982). New dates for the Tata, Hungary archaeological site. Nature 295, 590)1.

Scott, M. R. (1968). Thorium and uranium concentrations and isotope ratios in river sediments. Earth Planet. Sci. Lett. 4, 245)52.

Shirahata, H., Elias, R. W., Patterson, C. C. and Koide, M. (1980). Chronological variations in concentrations and isotopic compositions of anthropogenic atmospheric lead in sediments of a remote subalpine pond. Geochim. Cosmochim. Acta 44, 149)62.

Stirling, C. H., Lee, D.-C., Christensen, J. N. and Halliday, A. N. (2000). High-precision in situ ²³⁸U–²³⁴U–²³⁰Th isotopic analysis using laser ablation multiple-collector ICP–MS. Geochim. Cosmochim. Acta 64, 3737)50.

Thurber, D. L., Broecker, W. S., Blanchard, R. L. and Potratz, H. A. (1965). Uranium-series ages of Pacific atoll coral. Science 149, 55)8.

Veeh, H. H. and Burnett, W. C. (1982). Carbonate and phosphate sediments. In: Ivanovich, M. and Harmon, R. S. (Eds), Uranium Series Disequilibrium Applications to Environmental Problems, Oxford Univ. Press, pp. 459)80.

Walter, H. J., Rutgers van der Loeff, M. M. and Hoeltzen, H. (1997). Enhanced scavenging of ²³¹Pa relative to ²³⁰Th in the South Atlantic south of the Polar Front: implications for the use of the ²³¹Pa/²³⁰Th ratio as a paleoproductivity proxy. Earth Planet. Sci. Lett. 149, 85–100.

Winograd, I. J. (1990). Dating sea level in caves: comment. Nature 343, 217)18.

Winograd, I. J., Coplen, T. B., Landwehr, J. M., Riggs, A. C., Ludwig, K. R., Szabo, B. J., Kolesar, P. T. and Revesz, K. M. (1992). Continuous 500,000-year climate record from vein calcite in Devils Hole, Nevada. Science 258, 284)7.

Yang, H.-S., Nozaki, Y., Sakai, H. and Masuda, A. (1986). The distribution of ²³⁰Th and ²³¹Pa in the deep-sea surface sediments of the Pacific Ocean. Geochim. Cosmochim. Acta 50, 81–9.

Yokoyama, Y. and Nguyen H. V. (1980). Direct and non-destructive dating of marine sediments, manganese nodules, and corals by high resolution (-ray spectrometry. In: Goldberg, E. D., Horibe, Y. and Saruhashi, K. (Eds), Isotope Marine Chemistry. Uchida Rokkaku, Ch. 14.

Yu, E.-F. Francois, R. and Bacon, M. P. (1996). Similar rates of modern and last-glacial ocean thermohaline circulation inferred from radiochemical data. Nature 379, 689–94.

Zhao, J.-x., Xia, Q. and Collerson, K. D. (2001). Timing and duration of the Last Interglacial inferred from high resolution U-series chronology of stalagmite growth in Southern Hemisphere. Earth Planet. Sci. Lett. 184, 635–44.